Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$170.54	13.147%	$192.9609	$192.96	$192.95	$193.00
Purchase #2	$164.57	9.140%	$179.6117	$179.61	$179.60	$179.60
Purchase #3	$179.50	9.321%	$196.2312	$196.23	$196.25	$196.20
Purchase #4	$91.61	9.839%	$100.6235	$100.62	$100.60	$100.60
Purchase #5	$173.85	6.707%	$185.5101	$185.51	$185.50	$185.50
Purchase #6	$63.53	8.767%	$69.0997	$69.10	$69.10	$69.10
Purchase #7	$136.84	3.626%	$141.8018	$141.80	$141.80	$141.80
7 purchase totals =	$980.44		$1,065.8389	$1,065.83	$1,065.80	$1,065.80